K-casein

Chymosin (found in rennet) splits K-casein into an insoluble peptide (para kappa-casein) and water-soluble glycomacropeptide (GMP).

GMP is responsible for an increased efficiency of digestion, prevention of neonate hypersensitivity to ingested proteins, and inhibition of gastric pathogens.

Milk-clotting proteases act on the soluble portion, κ-casein, thus originating an unstable micellar state that results in clot formation.

However, milk clotting may take place without the participation of enzymes because of variations in physicochemical factors, such as low pH or high temperature.

At the same time, the classical method is not specific enough, in terms of setting the precise onset of milk gelation, such that the determination of the enzymatic units involved becomes difficult and unclear.

FTC-κ-casein allows the detection of different types of proteases at levels when no milk clotting is yet apparent, demonstrating its higher sensitivity over currently used assay procedures.